Sets a flash that will not be available to the next action, only to the
current.

flash.now[:message] = "Hello current action"

This method enables you to use the flash as a central messaging system in
your app. When you need to pass an object to the next action, you use the
standard flash assign ([]=). When you need to pass an object
to the current action, you use now, and your object will
vanish when the current action is done.

Entries set via now are accessed the same way as standard
entries: flash['my-key'].